Saponification of organic esters of cellulose



I Patented Sept. 7,

' UNITED s Ar-E'S? P TE T-name? ration of Delaware No Drawing. Application May 31 1935, SerialNo.

24,355. In Great Britain' June is, 1934 a 11 Claims. This invention relates to improvements in the saponification of organic esters of cellulose, and in particular to thesaponificaticn'of filaments;- threads, fibres, ribbons, films and like materials organic base. Thus it is of advantage in'treat- 5 comprising such esters.

U. S. application S. No. 709,335 filed 1stv February, 1934, describes the saponification of materials comprising cellulose acetate or other saponifiable ester of celluloseby means of liquid media. containing organic bases, and particularly bases such as methylamine. The specification indicates the advantages obtainable by the use of such bases over the use of mineral saponifying agents. Among'the most important of these advantages 5' are the enhanced extensibility coupled with high strength of the products and the relatively small loss of weight involved in effecting such a degree of saponification as substantially tochange the solubility properties and dyeing properties of the materials-for example to produce from ordinary celluloseacetate materials, materials which have an aflinity for cotton dyes, which are insoluble 'in acetone and which have an enhanced extensibility. Methylamine is particularly 'advantageous from this point of view.

U. S. application S. No. 752,376 filed 9th November, 1934, contemplates the saponification of inateri als of the type referred to above by'means of liquidsaponifying agentscontaining bases such as ethylene diamine, which have also been found particularly suitable where high tenacity coupled with relatively high extensibility. and small loss of weight on saponification are desired. U. S. applications S. Nos. 756,285 and 756,284

' filed on 6th December, 1934, disclose the remarkable acceleration'in saponification by means of methylamine, ethylene. diamine and like acting organic bases which can lee-obtained by, applying these bases in the presence of even relatively 40 small amounts of metals which are capable of forming amines or like complex nitrogen-containing compounds, and particularly inth'e' presence (ere-') tion is completed by a subsequent treatment with a mineral saponifying agent.

Preferablythe greater part of the saponification desired should be effected by means of the ing materials, containing 'twoor more acidyl groups per CsHioOs unit. so as to produce complete 'saponification or at least to saponify to a con.- siderable extent, for example until afiinity for cellulose ester dyes is lost, tocarry saponification. by means of the organic base to the stagewhere only '1.

to 1 acidyl 'groups per CeHicOs unit remain. The product so obtained is then treated with the mineral saponifying agent to complete the sap'onification. desired. 1

' The process of the invention enables results similar to those obtained by the use of methyl amine or like acting organic base alone to. be obtained much more rapidly than when the whole of the desired saponification is effected by means of such base alone. By the process of the invention filaments,- threads, fibres, ribbons, films and like materials may be obtained having an aflinity for cotton dyes, a high safe ironing point, high tenacity and good extensibility and elasticity.

The process enables substantially -complete saponification to be effected in a relatively short time.

' The process of the invention is of particular importance in connection with the .treatment of filaments, threads, fibres, ribbons, films and like materials of cellulose acetate, and'is described .herein with particular reference to the treatment of-suclr materials. The process is, owever,'ap plicable to the treatment of organic sters of cellulose, i. e. esters of cellulose containing organic acidyl groups, broadly. Among such esters other than cellulose acetate mention may be made of other simple esters example cellulose formate, propionate and butyrate, esters or higher fatty acid esters, for excellulose laurate, mixed fatty acid esters, for example cellulose acetate-propionate, cellulose acetate-butyrate and cellulose-acetate propionate-butyrate, ether-esters, for example ethyl cellulose acetate and oxy-ethyl cellulose acetate, and esters containng inorganic radicles, for example nitrocellulose acetate, nitrocellulose acetate-propionate and nitrocellulose acetate-butyrate. The ester content may bethat of a completely esterified cellulose. Preferably, however,

materials comprising esters of intermediate ester content, for example from 2 to 2 /2 ester groups per molecule, are employed. In 'the case of cellulose acetatafor example, it is preferable to of lower fatty acids, for.

employ acetates having an acetyl value between 48 and 58%, and preferably between 52 and 54.5% calculated as acetic acid per C6H1oO5 unit.

The materials treated may be in the form of filaments, threads, yarns, ribbons or the like or of fabrics containing such threads and the like. The organic ester of cellulose employed may be of normal or low viscosity, or of high viscosity, for example in the case of cellulose'acetate the viscosity may be of the order of 30 to 50, 100, 200 or even higher, these figures being obtained by comparison of a 6% solution of the ester in acetone at 25 C. with glycerine at the same temperature taken as a standard of 100. Such esters of high viscosity may readily be made by methods in which degradation of the cellulose molecule is substantially avoided during acidylation, for example the methods of U. S. Patent No. 1,708,787. On the other hand, the viscosity of the cellulose acetate employed may be of the order of 10 to 20 or even lower, or between 20 and 30 measured on the scale referred to above.

Any suitable dry or wet spinning method may be employed in producing the filaments and the like. Special mention may be made of the methods described in U. S. applications S. No. 402,785 filed 26th October, 1929, No. 418,414 filed 3rd January, 1930, No. 437,423 filed 20th March, 1930, No. 469,622 filed 21st July, 1930, and No. 601,043 filed 24th March, 1932, wherein the materials are produced by wet spinning methods in the course of which they are stretched to a considerable extent. The materials may also, particularly when spun by a dry spinning method, be subjected to a stretching treatment prior to saponification. Such treatments are particularly ethylamine.

valuable where a high tensile strength in the products is required, and for this purpose it is of advantage to stretch the materials to a considerable extent, for example to 200, 300 or even more than 500% of their original length. The stretching may be facilitated by any suitable means, e. g. by means of organic swelling agents or as described in U. S. applications S. No. 4,510 filed 1st February, 1935 and No. 4,511 filed 1st February, 1935 by means of steam or hot water.

The stretching may be eflected in a single stage or in several stages, with or without a rest interval between the stages, as described in U. S. application S. No. 573,424 filed 6th November, 1931. If desired after stretching and before saponification the materials may be treated with shrinking agents, as described, for example, in U.3S. application S. No, 611,240, filed'13th May, 19 2.

The organic saponifying agent preferably comprises an aqueous solution of methylamine. Other bases of a similar nature may howeverbe employed, among the most important of which is ethylene diamine. The invention moreover includes the use of other strong bases, for example ethylamine, propylamine, amylamine, and tri- Again, somewhat weaker bases of the same series, for example trimethylamine and allylamine, may be used. Further, considerably stronger bases of the same series may be employed, even very strong bases such as tetramethyl ammonium hydroxide, provided care be taken toavoid damaging the materials. The saponifying agent may moreover contain bases of the heterocyclic series, for example piperidine. Again, as described'in U. S. application S. No. 752,376, amines other than ethylene diamine containing more than one amino group,,and particularly aliphatic diamines of relatively-10W m0- lecular weight, for example symmetrical dimethyl ethylene diamine, mono-methyl ethylene diamine, and propylene diamine may also be used. Preferably at least one of the amino groups of such amines should be unsubstituted or mono-substituted. Amines containing more than two amino groups may also be employed, for example 1.2.3- triamino propane. The effect of one or more hydroxy groups in the amine appears to be to favour the penetration of the materials by the saponifying agent, and with this object in view substances of the type of wy-diamino-p-hydroxy propane may be used with advantage. The action of the organic base may be accelerated by the presence of appropriate agents, among which copper and copper salts are of particular importance, as described in U. S. applications S. Nos. 756,285 and 756,284. The presence of small quantities of caustic soda or other mineral alkali may also accelerate the action of the organic base.

The organic saponifying medium is preferably applied to the materials in the form of an aqueous solution. Generally speaking, aqueous concentrations of -30% are suitable. Naturally however the most suitable concentration at which a particular base can be employed will depend on the nature of that base. Concentrations below 15%, e. g. 10%, can also be used but in this case saponification isapt to be undesirably slow. The temperatures may range from below atmospheric temperature to the neighbourhood of the boiling point of the solution. Thus the temperature may be between 15 or C. and 25 or C. but more rapid saponiflcation occurs at somewhat higher temperatures, e. g. 30-60 C. or more. With a view to preventing excessive evaporation of the organic base saponification may be efiected under pressure as described below, or the surface of the saponifying medium may be covered with a layer of oil, wax or other suitable relatively non-volatile substance which is liquid at the temperature of working. Preferably when such substance is used the arrangement is such that the materials treated do not come into contact with-the substance. In general, the conditions should be chosen so that the desired degree of saponification may be effected by means of a treatment lasting from 30 seconds or even less up to 1 or 2 minutes. The materials should not be allowed to remain in contact with the saponifying medium after the desired degree of saponiflcation has been effected.

The mineral saponifying agent is preferably applied in aqueous or aqueous-alcoholic solution.

Where themineral saponifying medium contains an alcohol this may itself play a part in the saponification, so that a smaller amount of saponifying agent may be necessary than is theoretically required to give the desired saponification. Among the most useful of mineral saponifying agents is caustic soda. Other alkaline compounds of alkali metals which maybe employed are, for example, trisodium phosphate, sodium carbonate, sodium silicate, the corresponding potassium salts and potassium hydroxide. The concentration of the mineral saponifying agent may vary between wide limits. Concentrations of 1 or 2 to 4 or 5% caustic soda or the equivalent of other alkali are very suitable. Considerably lower concentrations may be employed, but in general this involves a more protracted treatment and/or the use of higher temperatures. The temperatures may be of the order of to 70 C., but in some cases, particularly when employing relatively low action upon the cellulose esters treated. Both the mineral saponifying agent and the saponifying agent containing the organic base may if desired contain swelling agents, other than alcohols, for' the cellulose esters; For example'these solutions may 3 contain acetone, the dimetliyl ether of glycol, dioxane, or methylene ethylene ether, all of which substances are swelling agents for cellulose acetate. I

The process of the invention is preferably carried out as a continuous operatiomthe materials being passed, for example, first through a bath containing the methylamine or other organic base and then through a bath containing the mineral saponifying agent. Between the two stages of such a treatment a washing step may if desired be interposed, but this will in general be unnecessary. When the materials are treated in the form of filaments, threads, yarns and the like it is of advantage to effect saponification in warp for- 4 mation, i. e. by drawing a warp, i. e. a number of threads in parallel relationship and in the same plane, through baths containing the saponifying agents by means of rollers or like devices extending across the entire warp.

The invention is not, however, limited to carrying out the process in the continuous manner described above.

Thus, for example, the mate rials in hank form may be suspended from rods which are caused to traverse in turn baths containing the organic and the mineral 'saponifying.

agents, the rods being caused at the same time to rotate so as to expose each portion of the yarn to the same depth in the bath for the same period. Agaimthe materials may be treated in the form of bobbins, cheeses or like packages, or in the form of cakes from centrifugal spinning boxes. Any suitable means may in fact be adopted in applying the saponifying agents to the materials. Materials in yarn or like form may be treated continuously with their production and/or with a stretching step. Again, in the case of such materials stretching may be effected during saponiflcation or, provided saponification has'not been carried too far,'aftersaponification, as described in U. S. application S. No. 755,232 filed 28th November, 1934. Thus, for example, a stretch may be imparted to the materials while they are in contact with the organic base, particularly if that base has a relatively strong swelling action upon the cellulose ester forming the base of the materials; or stretching may be effected while the materials are in contact with the mineral saponifying agent, provided a swelling agent is present therein.

The materials may be saponified in fabric form.

' This may conveniently be effected by passing the due. loss of saponifying agent. The pressure treatment may be applied whether the materials are'treated in the form of filaments, threads and the-like or of fabrics, and whether the process is is carried out continuously, the materials may be passed through a closed vessel containing the methylamine or other organic base in solution, under pressure, as described for example in U. S. application S..No. 11,080 filed 14th March, 1935. After leaving the vessel in which saponiflcatio'n with the organic base is effected 'the materials may pass through a second similar vessel containing'themineral 'saponifying agent; or this second vessel-may be open to the atmosphere.

It is of particular advantage toprovide the saponification vessel with end pressure chambers, as described in U. S. application S. No. 17,242 filed 19th April, 1935.

The materials prior to saponiflcation may be subjected to a treatmentadapted to facilitate penetration of the saponifying agent. This may comprise the application of water to the materials, or they may be treated with aqueous wetting agents, for example soaps.

The degree of saponification effected may be' merely suflicient to produce a loss in acidyl content of the order of 10 to 15% or even less, but is preferably somewhat higher, for example sufficient to remove 20 to 30 or 35% of the-original may be effected, sufficient to reduce the acetyl content by 40to or 60%. or more, even up to complete saponiflcation, according to the particular, purposein view. As indicated above it is of advantage when a high, degree of saponification is desired to reduce the acidyl content to a single acidyl group per CsHiioOs unit by-treatment with the organic base and then to complete the desired continuous or a. batchprocess. I When the process;

"acidyl content. Higher degrees of saponiflcation degree of'saponificati'on by means of the mineral saponifying agent. 1

The following examples illustrate the invention without limiting it in any way:--

Example 1 perature between 90 -C.-and the boiling point.

The yarn emerging from the second bath is washed dried and collected by suitable means.

The speed of travel of the yarn through the baths is adjusted so that by the time the second bath is reached the acetyl content is reduced to an amount corresponding withv one acetyl group per Cal-11005 unit, and so that the yarn is in contact with the methylamine bath for four or five times as long as with the caustic soda bath.

Example? The treatmentis carried out as in Example except that the treatment with methylamine is carried out under a pressure of 5-10 atmospheres at 80-110 C. the time of treatment being thereby shortened.

In these examples instead of methylamine other organic bases may be employed, e. g. ethylene diamine or ethylamine.- -The treatment may be carried out as a batch process instead of continuously as described.

What we claim and desire to secure by'Letters Patent is:-- L 1 I 1 Process for saponifying an organic ester of cellulose, wherein a part of the saponiflcation iseffected by treatment-with an organic base, and the desired saponification is completed by a subsequent treatment with a mineral saponifying agent.

2. Process for saponifying filaments, threads, fibres, ribbons, films and like materials having a 5 basis of'organic ester of cellulose, wherein a part of the saponification is eflfected by treatment with an aqueous liquid medium which contains a water-soluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom, and the desired saponification is completed by a subsequent treatment with a mineral saponifying agent.

l5 3. Process for saponifying filaments, threads, fibres, ribbons, films and like materials having a basis of cellulose acetate, wherein a part of the saponification is efiected bytreatment with an aqueous liquid medium which contains a watersoluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom, and the desired saponification is completed by a subsequent treatment with a mineral saponifying agent.

4. Process for saponifying filaments, threads, fibres, ribbons, films and like materials having a basis of organic ester of cellulose, wherein a part of the saponification is effected by treatment with a lower aliphatic amine, and the desired saponification is completed by a subsequent treatment with a mineral saponifying agent.

5. Process for saponifying filaments, threads, fibres, ribbons, films or like materials having a basis of cellulose acetate, wherein the materials are first treated with an aqueous solution of methylamine until the acetyl content corresponds to not more than one acetyl group per Cal-11005 unit, and the desired saponification is then completed by a subsequent treatment of the materials with an aqueous solution of a caustic alkali.

6. Process for saponifying filaments, threads,

fibres, ribbons, films or like materials having a basis of cellulose acetate, wherein the materials are first treated with an aqueous solution of ethylene diamine until the acetyl content corresponds to not more than one acetyl group per CsHioOs unit, and the desired saponification is then completed by a subsequent treatment of the materials with an aqueous solution of a caustic alkali.

'7. Process for saponifying filaments, threads, fibres, ribbons, films and like materials having a basis of cellulose acetate, wherein the materials are treated, first with a 15 to 30% aqueous solution of methylamine containing 0.05 to 0.5% copper at a temperature between 30 and C. until the acetyl content of the ester corresponds to not more than one acetyl group per CeHioOs unit, and the materials are then immediately treated with an aqueous solution containing 1 to 3% caustic soda at a temperature above C. until the acetyl content is. substantially completely removed.

8. Process forsaponifying filamentsythreads,

fibres, ribbons, films and like materials having a basis of organic ester of cellulose, wherein the saponification is partly efiected by treating the materials with a lower aliphatic amine until the cellulose ester contains not more than 1 acidyl groups per CeHmOs unit, and the desired saponification is completed by a subsequent treatment with a mineral saponifying agent.

' 9. Process for saponifying filaments, threads, fibres, ribbons, films and like materials having a basis of cellulose acetate, wherein a part of the saponification is effected by treatment with a lower aliphatic amine, and the desired saponification is completed by asubsequent treatment with a mineral saponifying agent.

10. Process for saponifying filaments, threads,

CERTIFICATE 0F CORRECTION.

' Septembe 7 1937 Patent No. 2,092,010.

ROBERT WIGHTON NONCRIEFF, ET AL.

ted specification certified that error zaqapears in the prin Page 1, second atent requiring correction as follows:

"or higher fatty acid esters,

and that the said Let-- It is hereby of the above nmnberedp column, line M1, for the words and syllable for ex read of higher fatty acids, for example; ters Patent should be read with this correction therein Q I e in the Patent Office.

conform to the record of the cas Signed and sealed this 2nd day of November, A. D. 1957.

Henry Van Arsdale I (Seal) Acting Commissioner of Patents.

that the same may 

